Initial Stage Growth and Electronic Structure of Al Overlayer on a Single-Domain Si(001)2×1 Surface

Abstract

Initial stage growth and electronic structures of Al overlayer on a wide-terrace single-domain Si(001)2×1 surface has been studied by low-energy-electron-diffraction (LEED) and photoelectron spectroscopy. The sequences of 2D phases found by LEED for Al coverages ≤ 0.5 ML at RT and 300°C are interpreted on the basis of an order-disorder transition of arrays of one-dimensional Al-dimer chains. The detailed electronic structure of 2×2 phase formed at ∼0.5 ML has been studied by angle-resolved photoelectron spectroscopy (ARPES) using synchrotron radiation. The existence and dispersions of five different surface states are identified for the first time, one at binding energies a little less than 1 eV and the others between 1 and 2 eV. The origin of the surface states can be interpreted in terms of the Al-dimer structures on Si(001).